This application relates to the art of cutting devices and, more specifically, to hand tools and blades therefor for cutting workpieces including those having a circular cross section such as plastic pipe or tubing, rubber hose, or other similar non-metallic materials. Although the preferred embodiments will be described in connection with a ratchet-type tubing cutter apparatus for cutting plastic tubes by hand and to a blade therefor, it is to be appreciated that the embodiments have application in other areas including a wide range of manual as well as powered devices for cutting, clipping, or otherwise applying forces to associated workpieces.
A wide variety of tubing cutters have been provided heretofore for cutting plastic tubing of the character used in commercial and domestic water systems, such as schedule 40 PVC tubing for example. Such cutters have included scissors-type cutters such as that shown in U.S. Pat. No. 6,513,245 to Aubriot and U.S. Pat. No. 6,658,738 to King wherein a tube to be cut is supported in a cradle portion of the cutter and a blade is displaceable about a fixed pivot axis to cut a tube interposed between the cradle and blade. In the King patent, the pivot axis is adjustable to accommodate the cutting of tubes of different diameter.
The scissors-type cutters which require a squeezing action of the handles require an excessive effort on the part of the user to achieve a cutting operation, especially with large diameter tubing. Partly in this respect, these tools require the user to rock or rotate the tube and cutter in opposite directions while squeezing the handles to apply a cutting load. Furthermore, with initially cutting through a larger diameter tube, a user who has a small hand span has difficulty in applying the necessary closing force on the handles to achieve initial cutting of the tube and, often, has to grasp the handles with both hands to initiate cutting.
Another type of tubing cutter heretofore available includes a cradle for supporting a tube to be cut and a pivotal cutting jaw or blade which is intermittently displaced toward the cradle by means of a ratchet mechanism. One such example is U.S. Pat. No. 4,368,577 to Babb which shows a tool having a blade rotatable in increments or steps from a retracted position in which the blade is enclosed within a housing, to a cut off position in which the blade cooperates with a stationary anvil so as to sever the article to be cut. A ratchet drive interconnects a movable handle and the blade so as to incrementally drive the blade toward its cut off position upon manipulation of the handle. A pawl prevents opening of the blade caused by the springiness of the article being cut upon being engaged by the blade. The blade is returned after cutting the object to its retracted position by releasing a thumb operated locking pawl. Other ratchet cutters have been proposed as well such as, for example, those shown in U.S. Pat. No. 4,312,127 to Tanaka and U.S. Pat. No. 4,674,184 to Anderson.
The ratchet mechanisms provided in the ratchet-type hand cutting tools described above allow a smaller stroke of the cutter handles relative to one another for each intermittent cut, whereby users without a large hand span can operate the cutter. However, the cutters are somewhat structurally complex particularly with respect to the mechanisms used for mounting of the cutter blades. Also, in these prior art device, blade maintenance including blade removal and replacement is cumbersome for the users. More particularly, the ratchet cutters described above must be first partially disassembled in order to remove and replace the cutter blade. Users of these tools have learned that this is not a quick or easy process. At best, some ratchet cutters require the removal of a blade screw/pin and a disconnection of a blade spring from attachment with the blade. Typically, the blade screws/pins are made of a threaded bolt and nut arrangement often including additional biasing and locking washers and springs to load against the blade. Further, additionally, the spring is often hooked or otherwise fastened onto the blade using a special connection and is typically held under tension in order to pre-load the blade in its returned or retracted position. Thus, when replacing or otherwise servicing the blade, the spring must be first stretched by some means and then connected with the blade. Again, typically, this is not an easy process, particularly when there is a need to replace the blade at a job site. Still further, oftentimes tools are needed together with adequate time and a fair amount of specialized experience in order to replace the cutting blade in typical ratchet tubing cutters.